Reports on an investigation on the behavior of high-strength concrete beams (with concrete compression strength equal to 11,600 psi or 80 MPa), with and without steel fiber reinforcement, to determine their diagonal cracking strength as well as nominal shear strength. Experimental data on the shear strength of steel fiber reinforced high-strength concrete beams are currently scarce to nonexistent. Twenty-two beam specimens were tested under monotonically increasing loads applied at midspan. The major test parameters included the volumetric ratio of steel fibers, the shear span-to-depth ratio, the amount of longitudinal reinforcement, and the amount of shear reinforcement. It was found that steel fiber reinforced high-strength concrete beams effectively resist abrupt shear failure. Such beams exhibit higher cracking loads and energy-absorption capabilities than comparable high-strength concrete beams without fibers. Empirical prediction equations are suggested for evaluating the diagonal cracking strength as well as nominal shear strength of steel fiber reinforced high-strength concrete beams.

Describes improvements in the performance characteristics of cements due to carbon fiber reinforcement. In particular, the structure, physical properties, mechanical behavior, and durability aspects of carbon-cement composites using pitch-based fibers are discussed. The various possible applications of these composites in structural and nonstructural applications are enumerated and future research needs to be identified.

It is well recognized that fiber reinforced concrete (FRC) exhibits a number of superior properties relative to plain concrete, such as improved strength, ductility, impact resistance, and failure toughness. These advantageous features of FRC can lead to novel structural applications, for which standard design and analysis procedures must be supplemented by numerical modeling (for example, the finite element method). This, in turn, makes necessary the development of satisfactory constitutive models that can predict the behavior of FRC under different load conditions, both monotonic and cyclic. In this paper, a constitutive model for FRC is developed loosely within the theory of mixtures. For plain concrete, an anisotropic, strain-based, continuum damage/plasticity model with kinematic and isotropic damage surfaces is developed. To represent the effect of the fibers, a simplified model that accounts for the tensile resistance of the fibers and the enhanced tensile resistance of the plain concrete is proposed. The predictions of the FRC constitutive model are compared to data from laboratory tests of steel fiber reinforced concrete (SFRC) specimens under uniaxial and biaxial loadings.

Carbon fiber reinforced cement composite (CFRC) has outstanding advantages in its dynamic characteristics and durability. Among other characteristics, it has a flexural strength three to four times higher than that of ordinary concrete. Taking advantage of these characteristics of CFRC in designing curtain walls, the manufacturing of thin, lightweight curtain walls becomes possible. This paper describes experimental studies conducted using CFRC specimens to examine the effects of mixing and placing conditions upon the flexural strength of CFRC, scale effects, and the fatigue of CFRC subject to repetitive loads. Furthermore, based on the results of these experiments, allowable bending stress in designing curtain walls was determined and its authenticity verified by having a full-scale composite panel undergo a wind resistance test. Several examples of CFRC used as curtain walls are also introduced.

Reports the results of an investigation on the strength and ductility of fiber reinforced high-strength concrete under direct shear. Both experimental and modeling studies were performed. In the experimental study, fiber reinforced high-strength concrete pushoff specimens were tested. Two fiber types, polypropylene and steel, were used with or without conventional stirrups. An existing model was further developed and used in the analytical prediction of the shear stress-strain relationships for these specimens. In general, fibers proved to be more effective in high-strength concrete than in normal strength concrete, increasing both ultimate load and overall ductility. This is attributed to the improved bond characteristics associated with the use of fibers in conjunction with high-strength concrete. For the specimens with steel fibers, significant increases in ultimate load and ductility were observed. With polypropylene fibers, a lower increase in ultimate load was obtained when compared to the increase due to steel fibers. Ductility of the polypropylene fiber reinforced specimens was greater than that of the steel fiber reinforced specimens. In the tests involving the combination of fibers and conventional stirrups, slight increases in ultimate load and major improvements in ductility were observed when compared to the values for plain concrete specimens with conventional stirrups. In general, good agreement between the model and the test results was found.